Many basses, vintage guitars, and guitars with more than one neck (doublenecks), have necks that are heavier than the instrument bodies they are joined to. In these instances, when a player of an unbalanced instrument releases both hands from the instrument, they lose control over the instrument. The result is the neck of the instrument “drops” or “dives”. Attention dedicated to this problem has focused primarily on what the neck is doing: dropping in height. However, we concerned owners of these unbalanced guitars and basses were focusing on the wrong end of the instrument. We looked endlessly at the guitar or bass “neck”, and its heavy head stock and tuners, and wondered how we could prevent it from “falling”. No adequate solution has ever presented itself by looking at and focusing on “the neck”. But what else was there to look at? As soon as I asked that question, the current embodiment of this invention slowly came into view, and the creation of The Neckdive Strap began to take form. What if we turn the problem “on its head”, and start thinking in “opposites”? If something is “falling”, it stands to reason that somewhere else, something is “rising”. It then stands to reason that as the neck of the instrument is “falling” in height, the opposite end of the instrument is “rising”. Upon observing this phenomenon, it became apparent that if an instrument body's furthest and opposite end-point from the neck could be prevented from rising, the neck would no longer drop, or “dive”, when a player released both hands from the instrument. The standard shoulder strap end pin (FIG. 1, #3) was observed to be the optimal location for some kind of strap to prevent this “rise”. Upon further investigation, this strap could use a player's leg to provide the anchor point. A prototype was made from an old pant belt, and accomplished the sought after results. The current embodiment has added features of a quick release leg buckle (4), two adjustable buckles for leg girth (4) and strap length (5), and an option for using an off the shelf strap lock to connect the strap end hole (3a) to the instrument end pin (3).